toots: I think the danger is confusing patriotism with nationalism.
Patriotism is the love of one’s country and the recognition that countries, like people, make mistakes, or lose their way or forget what really matters.
Nationalism, on the other hand, is the bunch of us sitting around a bonfire of burning books and singing “Deutschland Uber Alles”.
Subtle difference, but important.
You don’t have to justify your patriotism to anyone for the simple reason that everyone’s explanation is different. And that is what makes America truly great.